Re: Simcity won't install on my mac.

Hi @LizAnne99  -  Apple dropped support for 32-bit games like SimCity, beginning with MacOS Catalina 10.15. There is more information in this post: https://answers.ea.com/t5/SimCity-2013/Mac-SimCity-and-MacOS-Catalina/m-p/8298578#M127940 , including some options for running 32-bit games after upgrading to Catalina. 

Since you recently purchased the game, if none of the above options appeal to you, you might want to check out the Great Game Guarantee.